
Maybe my generalization is off, but, I doubt anyone would be naming any files after the handful of variables that exist as default ENV vars.
Almost everyone trying to use %somevar%\foo\bar in TC's Move/Rename/Command/Param/Command-Line(etc) fields are expecting variable expansion.
So if you make the rule consistent.
1) %String% is always expanded, if it exists as a variable.
2) %"String"% is literal, quotes break attempts to expand.
3) %% Sends 1 literal percent sign.
4) "%" Sends 1 literal percent sign.
Quotes are an illegal character for Files/Folders.
Thus you have this:
* Attempt expansion of any percent-enclosed strings that don't contain quotes.
* If variable doesn't exist, the percent-enclosed string is literal.
People are used to needing to quote paths/files that have spaces in them (in various places).
Except for #3 - The rules are consistent with command-line.
Explaining this in the help should be fairly straight forward:
If you wish to use percent-enclosed strings, enclose the string in quotes to prevent variable expansion.
Show %"TEMP"%, %"TMP"%, %TEMP% as examples.
If the %"quote"% option is a workable solution. Put it up for a vote on which people would prefer? Consistent with CMD Prompt or the inverse as MVV said?
Personally I believe with the quote options, #3 is not needed and is even possibly confusing. But it seemed like at least a few ppl thought it was a good solution.